Objectives. Mylene T. Truong, MD. Malignant Pleural Mesothelioma Background

Transcription

1 Imaging of Pleural Tumors Mylene T. Truong, MD Imaging of Pleural Tumours Mylene T. Truong, M. D. University of Texas M.D. Anderson Cancer Center, Houston, TX Objectives To review tumors involving the pleura with an emphasis on mesothelioma To describe the role of PET/CT in the staging of mesothelioma and factors that determine resectability To review recent trends in treatment of mesothelioma Benign meso, localized meso, solitary fibrous meso, LFTOP M = F, y.o. 50 % asymptomatic, but HPO and hypoglycemia 80% arise from visceral pleura Often pedunculated, surgery, 10% recurrence Rosado-de-Christenson; Radiographics, 23(3):759-83, 2003 Sensitivity Specificity Circumferential Distribution 100% 41% Pleura >1cm Thickness 94% 36% Nodular Morphology 94% 51% Pleural fluid or pleural implants Involves visceral and parietal pleura Cytology positive: % Primary: lung most common, lymphoma, breast, pancreas, stomach, ovary, melanoma Background 88

2 Tumor Histology Staging Evaluation of MPM The primary imaging modality used in the diagnosis, staging, and treatment management of malignant pleural mesothelioma is CT. CT can assess for involvement of the chest wall, diaphragm, lungs, and mediastinum. Contrast enhanced CT shows circumferential nodular right pleural thickening and right hilar (arrow) and subcarinal adenopathy (asterisk). SUNDAY * Staging Evaluation of MPM CT is readily available and most frequently used in evaluating patients for surgical resection, and findings that preclude surgery include metastatic disease to the: Staging: MRI vs. CT MRI is superior to CT in accuracy of evaluation for invasion of endothoracic fascia or a single chest wall focus of involvement (MRI 69% vs. CT 46%). Note the obliteration of the endothoracic fascia and extrapleural fat plane (arrow) adjacent to the right pleural mass. Staging: MRI vs. CT vs. Laparoscopy Although MRI is superior to CT in accuracy for evaluation of diaphragmatic invasion (MRI 82% vs. CT 55%), extended surgical staging with direct visualization of the undersurface of the diaphragm with laparoscopy and peritoneal lavage can detect small volume disease missed on MRI. Staging: PET/CT PET/CT allows precise anatomic localization of areas of increased FDG uptake and can be useful in guiding biopsy of these sites. FDG avid foci in the bilateral supraclavicular regions (arrows) are suspicious for N3 disease and prompted node biopsy. 89

3 Staging: PET/CT The strength of PET/CT in staging is the detection of extrathoracic metastases. PET/CT identified occult metastases in 25% of patients being evaluated for surgery in one study. In more than half of these patients, extrathoracic metastases were not identified by routine clinical and conventional radiologic evaluation. PET/CT shows left MPM with solitary metastasis to right proximal humerus (arrow). No lytic or blastic lesion seen on CT. Staging and Resectability T2 Tumor involving each ipsilateral pleural surface with at least one of the following features: involvement of diaphragmatic muscle confluent visceral pleural tumor (including fissures) extension of tumor from visceral pleura into underlying pulmonary parenchyma 90

4 Chemotherapy Standard of care for first-line systemic therapy for MPM is cisplatin and pemetrexed, a multitargeted antifolate. In a multicenter phase III study of 448 patients, this combination had an objective response rate of 41% and improved overall survival by 3 months. CT shows response to therapy of right nodular pleural thickening (arrow). Surgery Extrapleural pneumonectomy (EPP) is the radical en bloc resection of the lung, pleura, diaphragm, and pericardium. Fusion of the pleura at the central tendon of the diaphragm and the lateral portion of the pericardium mandates resection and subsequent reconstruction with a prosthetic patch. Pleurectomy and decortication (P/D) is a lung-sparing operation in which the diseased pleural envelope that encases and constricts the lung is mobilized off the chest wall, mediastinum, diaphragm and pericardium, and then stripped from the surface of the lung. SUNDAY Ongoing debate in terms of which is the preferred surgical approach. Although EPP is associated with a higher morbidity (25%) and surgical mortality (4 15%), it provides more complete tumor cytoreduction than P/D, and the empty thorax permits the use of high-dose radiotherapy postoperatively. In contrast, P/D is associated with lower morbidity and mortality (1 5%), but complete tumor cytoreduction is less frequently attainable. Surgery Intensity Modulated Radiation Therapy (IMRT) Following Surgery for Local Control Sarcomatoid histology and the presence of positive extrapleural nodes usually preclude surgery. Favorable outcome is characterized by minimal or limited local regional disease, disease-free incomplete fissures, and epithelial histology. The region of the removed pleura is contoured by the radiation oncologist in consultation with the surgeon to carefully delineate appropriate target volumes to include all involved pleural surfaces, ipsilateral mediastinal lymph nodes, the retrocrural space, and the deep margin of the thoracotomy incision. Multiple beams and inverse planning are used to treat the region at risk to the same dose of 45 Gy in 25 fractions while placing dose constraints on normal structures such as the heart, kidney, spinal cord, and stomach. Negative prognostic factors for survival include involvement of lymph nodes outside the pleural envelope and tumor detected at the parietal, mediastinal, diaphragmatic, and pericardial resection margins. Conventional anatomic imaging is an integral component in the evaluation and management of patients with benign and malignant pleural diseases. Conclusion PET/CT and surgical staging procedures are useful in improving the accuracy of clinical staging of malignant pleural mesothelioma. 91

5 References 92